132 



REPORT OF STATE GEOLOGIST. 



Above the clypeus, is a ridge extending upward along the median 

 line of the face to the vertex. This is the "frontal cosla;" and its 

 characters are often used in classification. In one species it may be 

 sulcate or grooved; in another, flat. Its edges, or "carincB" may be 

 parallel the full length or may diverge or converge. Its width and 

 prominence are also often mentioned. 



The region on the side of the head, ])eliiii(l the eye, and a])ove the 

 base of the mandibles is the cheek or "(jena" ((jcn.). To its inner wall 

 is attached the large muscle which moves the mandible. 



The eyes of a locust are five in number; two large compound ones, 

 and three small, simple ones. The compound eyes are present in all 

 Orthoptcra. In the locust they vary in shape, but for the most part 

 are oval, and are located on the upper portion of the sides of the 

 head. Each is made up of many thousands of six-sided facets or 

 lenses, in each of which a single filament of the optic nerve ends. 

 The simple eyes or "ocelli'- (oc.) are absent in some Orthoptera, as 

 the Locustidoe, but are present in the locust. Two of theni are situ- 

 ated just above the base of the antenna} close to the inner margins 

 of the compound eyes; while the third is located near the middle 

 of the frontal costa. Their position varies in the different families 

 of Orthoptera. These ocelli are thought to be inherited from the 

 obscure eyes of the worm-like ancestry of the locust, while the many 

 facetted compound eyes of insects and crustaceans have been evolved 

 to satisfy the needs of the more recent existence of these groups. 



The antenna; (ant.) of the locust are simple, many jointed appen- 

 dages, located on the face betAveen the eyes and articulating witli the 

 licad by a ball and socket joint. They are princi- 

 1^ ]>al]y organs of touch, but are also supposed to con- 



tain tlie nerves of snu'll. They vary much in length 

 iind form among the different families of Orthop- 

 tcra. tlio variation being the result of adaptation 

 to jlu'ir peciiliiir surroundings and habits. For in- 

 stance, in those Locustidto which dwell in caves 

 ihcy are very much longer than in those members 

 of tlic same genus which dw(>ll aliove ground. Cbar- 

 actci-s ])ertaining to their form. lengt-Ji, and i)oint of 

 union witli tlu' head, arc inucli used in classification, 

 ■filiforni,'" "clavate,'' "setaceous," etc., relating to 

 their form, are deliui'd in the accompanying glossary. 



Characters pertaining to the vertex, or that part of the epicranium 

 between the eyes, are much used in separating the different species of 

 Orthoptera. The central portion of the vertex, known as the "disk" 



¥\g. 5 SliowiiiK 

 f n 8 t i gi u 111, disk 

 and foveola of ver- 

 tex. 



(Alter Ludpor.^ 



Such terms a? 



